Alarm and safeguard system for a controlled environment box

ABSTRACT

An alarm and safeguard system is disclosed which is particularly adapted for use with an automatically operated, controlled environment box, usually referred to as a &#39;&#39;&#39;&#39;dry box.&#39;&#39;&#39;&#39; A manometer partly filled with mercury is in direct communication with the dry box and is electrically connected to a power source and to an electromagnetic relay. If the pressure in the dry box atmosphere drops below or rises above a pre-set safe operating level, the mercury in the manometer will contact one of the electrical connections to the relay and thereby energize the relay. Energizing of the relay completes a circuit through an alarm system comprising a buzzer and a light. Activation of the buzzer and the light thereby provides both an audible and a visible signal which draws attention to the abnormal pressure condition in the box.

United States Patent Staudacher et al.

[54] ALARM AND SAFEGUARD SYSTEM FOR A CONTROLLED ENVIRONMENT BOX [72]Inventors: Gerald R. Staudacher, Bay City; Sidney W. Ames, Midland, bothof Mich.

[73] Assignee: The Dow Chemical Company,

Midland, Mich.

[22] Filed: Jan. 29, 1971 [21] Appl. No.: 110,805

[52] US. Cl. ..137/554, 23/281, 55/274 [51] Int. Cl.....G04c 23/00, G05b19/00, CO6b 21/02 [58] Field of Search .137/554, 557; 23/281; 317/142;

[56] References Cited UNITED STATES PATENTS 3,474,823 10/1969 Finlaysonet a1 ..137/554 Power- Source 110V Mfercfianye [451 Nov. 21, 1972Primary ExaminerHenry T. Klinksiek Attorney-Griswold 81. Burdick, V.Dean Clausen and Lloyd S. Jowanovitz [57] ABSTRACT An alarm andsafeguard system is disclosed which is particularly adapted for use withan automatically operated, controlled environment box, usually referredto as a dry box. A manometer partly filled with mercury is in directcommunication with the dry box and is electrically connected to a powersource and to an electromagnetic relay. If the pressure in the dry boxatmosphere drops below or rises above a preset safe operating level, themercury in the manometer will contact one of the electrical connectionsto the relay and thereby energize the relay. Energizing of the relaycompletes a circuit through an alarm system comprising a buzzer and alight. Activation of the buzzer and the light thereby provides both anaudible and a visible signal which draws attention to the abnormalpressure condition in the box.

5 Claims, 1 Drawing Figure /n/erc/10n9e con/rol/er Vacuum Z7 oam oPATENTED nnv 2 1 I972 INVENTORS.

N QM ALARM AND SAFEGUARD SYSTEM FOR A CONTROLLED ENVIRONMENT BOXBACKGROUND OF THE INVENTION The invention relates broadly to controlledenvironment boxes. More particularly, the invention covers an alarm andsafeguard system for controlled environment boxes, particularlyautomatically operated boxes, wherein an abnormal pressure condition inthe box will activate an audible and visible warning alarm.

A controlled environment box, which may also be referred to as a drybox, inert atmosphere box, or glove box, is usually employed for thereaction or storing of materials which require a substantially dryenvironment, i.e., an environment relatively free of oxygen andmoisture. A typical example of the use of a controlled environment boxis in the preparation of pyrophoric compounds, such as certain metalhydrides, which will spontaneously ignite if exposed to oxygen andmoisture present in the surrounding atmosphere. To provide a suitableenvironment for preparing the hydride compounds, the atmosphere in theclosed box usually comprises a relatively chemically inert gas, such asnitrogen, which is substantially free of oxygen and moisture.

For most operations the pressure of the inert gas atmosphere in theclosed box is usually maintained at about the level of the surroundingatmosphere. To maintain the box pressure at the desired operating level,the flow of inert gas into and out of the box is preferably regulated byan automatic electro-mechanical system which utilizes solenoid valves,pressure switches, and the like. For various reasons, however, such as amalfunction or failure in the equipment, an operator error, or the like,the inert atmosphere pressure in the box may drop below or rise above asafe operating level. The obvious undesirable result is a condition ofunderpressure or overpressure, which may cause the box to implode orexplode and thereby expose the contents of the box to the atmosphere.Another disadvantage is that a substantial amount of down" time andlabor time is usually required to repair or replace damaged equipment.

SUMMARY OF THE INVENTION A principal object of the present invention isto provide a controlled environment box incorporating an automatic alarmsystem which will give an immediate indication of an abnormal pressurecondition in the box atmosphere.

Another object is to provide an automatic alarm system of the typedescribed which will instantly shut down all electrical power to the boxsystems to prevent continued operation of the box until the malfunctionhas been corrected.

Still another object is to provide an alarm system of the type describedwhich incorporates both an audible signal and a visible signal toindicate that an abnormal pressure condition exists in the boxatmosphere.

The alarm and safeguard system of this invention includes a mainelectrical power source, which is electrically connected into a poweroutlet. The power outlet, in turn, supplies power to a valve means forcontrolling inert gas flow into and out of the box and to an interchangechamber associated with the box. A pressure sensing device communicateswith the environment box and is electrically connected into the mainpower source and into a relay. The relay, in turn, is connected .intothe main power source and into an alarm system. When the pressure of theinert atmosphere in the box 0 alarm system is completed, to therebyactivate the alarm system.

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE of the drawing is aschematic view of a controlled environment box, which includes an alarmand safeguard system, according to one embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, thenumeral 10 designates generally a controlled environment box. Mounted atone end of the box 10 is an interchange chamber 11. Chamber 11 isusually a cylindrical chamber with an inner door 11a which opens intothe box 10 and an outer door 11b, which opens to the surroundingatmosphere. Both of the doors are hingeably mounted on chamber 11 andeach door operates independently of the other. Each door is equippedwith a wheel-type latch or other suitable latch mechanism to form anairtight seal when the door is closed. The purpose of chamber 11 is toprovide an air-tight chamber through which materials can be moved intoand out of box 10.

Communicating with environment box 10 are branch lines 12 and 13, eachof which connect into a main line 14. Also branching off from main line14 are lines 15 and 16, which communicate with interchange chamber 11.The opposite end of main line 14 connects into a source of inert gas,such as nitrogen (not shown). In the automatic operation of box 10 theflow of inert gas into the box is preferably regulated by a solenoidvalve 17 in line 13. The solenoid valve 17 is opened and closed by apressure switch 18, which is electrically connected to valve 17 throughleads l9 and 20. Switch 18 also communicates directly with theenvironment box 10 through tube 21 and the switch is electricallyconnected to a power outlet panel 22 through leads 23 and 24. Aconventional bellows-actuated microswitch, of the type sold under thename Meletron, is preferred.

In certain instances, such as where a malfunction may occur in solenoidvalve 17 or pressure switch 18, the flow of inert gas into box 10 may beregulated manually by a valve 25 in branch line 12. Again referring tothe automatic operation of box 10, the inert gas flows out of the boxthrough a branch line 26, which connects the box with a main line 27.The opposite end of main line 27 connects into a vacuum pump 28, thepump being electrically connected to the power outlet panel 22 by leads77 and 78. A solenoid valve 29 in line 26 automatically regulates theoutflowing gas, the valve being controlled by pressure switch 30, whichis electrically connected to the valve by leads 31 and 32.

Switch 30 also communicates with box 10 through tube 33 and iselectrically connected to power panel 22 through leads 34 and 35.Pressure switch 30 is preferably a bellows-actuated micro-switch of thesame type as switch 18, described above. A branch line 36 alsocommunicates with box and connects into main line 27. If a malfunctionshould occur in solenoid valve 29 or pressure switch 30, the outflow ofgas from box 10 may be directed through line 36 and controlled by amanually operated valve 37 in line 36.

Evacuation of purge gas from interchange chamber 11, by vacuum pump 28,is through branch line 39, which communicates with chamber 11 andconnects into main line 27. A solenoid valve 40 in line 39 automaticallyregulates the gas being evacuated from chamber 11. The flow of inert gasinto interchange chamber 11, during purging of the chamber, isautomatically regulated by a solenoid valve 38 in branch line 16. Bothof the solenoid valves 38 and 40 are opened and closed automatically byan interchange controller 41, which controls the evacuation and purgesequence. Electrical leads 42, 43, connect solenoid valve 38 to thecontroller 41 and leads 44, 45, connect solenoid valve 40 to thecontroller.

Electrical power to the interchange controller 41 is supplied from poweroutlet 22 through leads 46 and 47, which connect the controller to thepower outlet. To simplify the present disclosure, the construction andoperation of controller 41 are not described herein.

However, a typical controller unit which may be used in the evacuationand purging of interchange chamber 11 is specifically described in US.Pat. No. 3,474,823, to Finlayson and Dean.

lf a malfunction should occur in the controller 41, the evacuation andpurging of interchange chamber 11 with inert gas may be done manually.In a manual evacuation, the inert gas is drawn out of chamber 11 throughbranch line 48, which connects chamber 11 with main line 27. Theoutflowing gas is regulated by a manually operated valve 49 in line 48.To manually purge interchange chamber 11, the purge gasis directed intothe chamber through branch line 15, with the gas flow being regulated bya manually operated valve 50.

A manometer 51 provides a device for sensing a deviation in the pre-setpressure level of the inert gas atmosphere in environment box 10.Basically, manometer 51 comprises a U-shaped glass tube having a closedleft leg 51a and an open right leg 51b, the legs being partly filledwith mercury 52. The manometer communicates with environment box 10through a tube 53, which connects the box with closed leg 51a. A mainelectrical lead 54 connects the manometer with a main power source 55.

A first sensing wire 56 is encased in closed leg 51:: of manometer 51.Wire 56 is positioned in leg 51a so that the lower end of the wire willnot contact the mercury 52 until the inert gas pressure in box 10 dropsbelow a pre-set level. A second sensing wire 57, which is inserted inopen leg 51b of manometer 51, is positioned such that the lower end ofthe wire will remain out of contact with mercury 52 until the inert gaspressure in box 10 rises above the pre-set level. Both of the sensingwires 56 and 57 are connected through a common lead 58 into one side ofa coil 59 in a relay 60. The opposite side of coil 59 is connected by alead 61 into a main power lead 62. The main lead 62, in turn, connectsthe main power source 55 with power outlet 22.

Relay is an electromagnetic relay of the type generally referred to asan alarm relay, which includes a holding circuit. More specifically,-therelay 60 is a three-pole, double throw relay, which has one circuitnormally closed and two circuits normally open. Any of the commerciallyavailable three-pole, double throw relays, of the type described above,and which include a holding circuit, may be used. Basic components ofrelay 60 are a magnet coil 59 and a three-pole armature 63. As shown inthe drawing, the relay is de-energized and is, therefore, in thenormally open position. in the normally open position of the relay, apower circuit is completed from main power source 55 through main lead54, branch lead 64, and through lead into power outlet 22.

When the inert atmosphere pressure in environment box 10 is at a normallevel, relay 60 will remain in normally open position. in the normallyopen position, the power circuit will remain closed and the other twocircuits in the relay, which comprise an alarm circuit and a holdingcircuit will remain open. The alarm system comprises a buzzer 66, as anaudible signal, and a light bulb 67, as a visible signal. One side ofthe audible alarm circuit is provided by branch lead 68, which connectsrelay 60 into main lead 54. The other side of the audible circuit isthrough common lead 69 and branch lead 70, which connect the relay tobuzzer 66, and through branch lead 71, which connects the buzzer intomain lead 62. One side of the visible alarm circuit is through commonlead 69 and branch lead 72, which connect light 67 to relay 60. Theopposite side of the circuit is through branch lead 73, which connectslight 67 into main lead 62.

One side of the holding circuit is provided by a branch lead 74, whichconnects relay 60 into main lead 54, through a re-set switch 75. Theopposite side of the holding circuit is through a lead 76, whichconnects relay 60 into common lead 58. When the inert at mospherepressure in environment box 10 deviates from the pre-set normalcondition, as explained more fully hereinafter, the armature 63 in relay60 will move from the normally open to the closed position. Whenarmature 63 moves to the closed position, it breaks the power circuitand simultaneously closes both the alarm and holding circuits.

In a typical operation of environment box 10, the pressure of the inertgas atmosphere is kept at about normal atmospheric pressure for safeoperation. To maintain the box pressure at a safe level, the lowpressure switch 18 is set for actuation at a minimum pressure level.Conversely, the high pressure switch 30 is set for actuation at amaximum pressure level. If the pressure in box 10 drops below theminimum setting, the bellows-actuated pressure switch 18 will opensolenoid valve 17, which allows nitrogen gas to flow into box 10 throughbranch line 13. As soon as the gas pressure in box 10 rises above theminimum setting, i.e., it comes up to the normal pre-set pressure,switch 18 will close valve 17, which allows the box to continue tooperate at a safe pressure level. Conversely, if the pressure in box 10rises above the maximum level, the pressure switch 30 will open solenoidvalve 29. As valve 29 opens, the vacuum pump 28, which runscontinuously, will draw inert gas out of box 10, through lines 26 and27, until the box pressure drops back to a safe operating level.

To illustrate the practice of the invention, assume that a malfunctionor failure occurs in high pressure switch 30, while solenoid valve 29 isopen. Such a condition can occur, for example, if dirt or other foreignmatter should get into the valve mechanism. If the failure should occurwhen the operator is not present to correct the problem, the vacuum pump28 will continue to run and therefore continuously withdraw inert gasfrom box 10. In this situation, the box pressure will drop below theminimum safe level in a very short time and may cause the box toimplode.

The alarm and safeguard system of this invention will prevent thehazardous underpressure condition described above. For example, as thepressure in box begins to drop below the normal pre-set level, the levelof the mercury 52 in leg 51a of the manometer will rise, due to thepartial vacuum which is created in the closed space above the mercury.Since the lower end of sensing wire 56 is positioned immediately abovethe normal" level of the mercury in leg 51a, the mercury will contactthe wire before the inert atmosphere in box 10 drops below the unsafepre-set level. When the mercury 52 contacts wire 56, a circuit iscompleted from power source 55, through manometer 51, and into relay 60.

As the circuit is completed from manometer 51 to relay 60, the armature63 will move from the normally open position to the closed position,thereby breaking the power circuit which feeds into power outlet 22.Breaking of the power circuit immediately shuts down all of theautomatic systems which control the operation of box 10, i.e., thesolenoid valves, pressure switches, the interchange controller and thevacuum pump. At the same time that the power circuit is broken, thealarm circuit and holding circuit will be closed, thereby actuatingbuzzer 66 and light 67 to provide both an audible and a visible warningsignal.

The purpose of the holding circuit, therefore, is to keep the alarmcircuit alive, so that buzzer 66 and light 67 will continue to emit asignal even if the mercury in manometer 51 is no longer in contact withthe sensing wire 56. This assures that the operators attention will beattracted to the malfunction which originally created the abnormalpressure condition in box 10. A situation could occur, for example, inwhich the pressure in box 10 may temporarily return to a normalcondition, i.e.,-within the minimum and maximum settings of pressureswitches 18 and 30. This pressure condition would allow the mercury 52to break contact with sensing wire 56. In the situation as described, ifthe relay 60 did not include a holding circuit, the relay wouldde-energize and thus close the power circuit. Once the malfunction inthe box system has been corrected, however, and the holding circuit isno longer required, the relay 60 may be de-energized by pushing re-setswitch 75.

It will be apparent from the above description of the alarm andsafeguard system of this invention, that the system will also providewarning of an unsafe overpressure condition in the environment box 10.For example, if the pressure in box 10 rises above the maximum pre-setlevel, the excess pressure will force the mercury 52 in manometer 51 upinto leg 51b. When the mercury in leg 51b contacts sensing wire 57, acircuit will be completed from manometer 51 to relay 60, therebyenergizing the relay to break the power circuit and simultaneously closethe alarm and holding circuits.

What is claimed is:

1. An alarm and safeguard system for a controlled environment box whichincludes, in combination:

a. a main electrical power source;

b. a power outlet which is electrically connected to the main powersource, to a valve means for controlling inert gas flow into theenvironment box, to a valve means for controlling inert gas flow out ofthe environment box, and to an electrical system which controls aninterchange chamber associated with the environment box;

c. a pressure sensing means which communicates with the environment box,is electrically connected to the main power source, and is adapted tosense a pressure condition in the environment box which does notcorrespond to a pre-set pressure condition;

d. a relay means which is electrically connected to the pressureindicating means and to the power outlet;

e. an alarm system which is electrically connected to the relay and tothe main power source; whereby, when the pressure in the environment boxassumes a level other than the said pre-set pressure condition, thepressure sensing means will actuate the relay, thereby interrupting thecircuit to the power outlet and completing a circuit through the alarmsystem, thus activating the said alarm system.

2. An alarm and safeguard system for a controlled environment box whichincludes, in combination:

a. a main electrical power source and a power outlet which connects intothe said main source;

b. a gas inlet line in communication with the environment box and asource of inert gas;

c. a gas outlet line in communication with the environment box and avacuum pump, the pump being electrically connected to the power outlet;

d. a first solenoid valve located in the gas inlet line and a secondsolenoid valve located in the gas outlet line;

e. a first pressure switch which communicates with the environment boxand is electrically connected to the first solenoid valve and the poweroutlet, for controlling inert gas flow into the environment box;

f. a second pressure switch which communicates with the environment boxand is electrically connected to the second solenoid valve and the poweroutlet, for controlling inert gas flow out of the environment box;

g. an interchange chamber in communication with the environment box;

h. an electrical control system connected to the interchange chamber andto the power outlet, for controlling evacuation and purging of theinterchange chamber;

i. a manometer in communication with the environment box and which iselectrically connected to the main power source;

j. an electrical relay which is connected to the main power source andthe power outlet;

k. a first electrical sensing means, which is associated with themanometer and is connected to the relay, for indicating a pressurecondition in the environment box which does not correspond to a pre-setpressure condition;

. a second electrical sensing means which is associated with themanometer and is connected to the relay, for indicating a pressurecondition in the environment box which does not correspond to the saidpre-set pressure condition;

in. an alarm system which includes an audible signal 3. The alarm systemof claim 2 in which:

a. the manometer is a Ushaped manometer having one closed leg and oneleg open to the outside atmosphere;

b. each leg of the manometer is partially filled with mercury;

c. a first sensing wire is encased in the closed leg of the manometerand positioned such that the mercury in said leg will contact thesensing wire and thus actuate the relay if the pressure in theenvironment box falls below the pre-set level;

d. a second sensing wire is encased in the open leg of the manometer andpositioned such that the mercury in said leg will contact the sensingwire and thus actuate the relay if the pressure in the environment boxrises above the pre-set level.

4. The alarm system of claim 2 in which the audible signal is anelectric buzzer.

5. The alarm system of claim 2 in which the visible signal is anelectric light.

Inf-007 m 1

1. An alarm and safeguard system for a controlled environment box whichincludes, in combination: a. a main electrical power source; b. a poweroutlet which is electrically connected to the main power source, to avalve means for controlling inert gas flow into the environment box, toa valve means for controlling inert gas flow out of the environment box,and to an electrical system which controls an interchange chamberassociated with the environment box; c. a pressure sensing means whichcommunicates with the environment box, is electrically connected to themain power source, and is adapted to sense a pressure condition in theenvironment box which does not correspond to a pre-set pressurecondition; d. a relay means which is electrically connected to thepressure indicating means and to the power outlet; e. an alarm systemwhich is electrically connected to the relay and to the main powersource; whereby, when the pressure in the environment box assumes alevel other than the said pre-set pressure condition, the pressuresensing means will actuate the relay, thereby interrupting the circuitto the power outlet and completing a circuit through the alarm system,thus activating the said alarm system.
 1. An alarm and safeguard systemfor a controlled environment box which includes, in combination: a. amain electrical power source; b. a power outlet which is electricallyconnected to the main power source, to a valve means for controllinginert gas flow into the environment box, to a valve means forcontrolling inert gas flow out of the environment box, and to anelectrical system which controls an interchange chamber associated withthe environment box; c. a pressure sensing means which communicates withthe environment box, is electrically connected to the main power source,and is adapted to sense a pressure condition in the environment boxwhich does not correspond to a pre-set pressure condition; d. a relaymeans which is electrically connected to the pressure indicating meansand to the power outlet; e. an alarm system which is electricallyconnected to the relay and to the main power source; whereby, when thepressure in the environment box assumes a level other than the saidpre-set pressure condition, the pressure sensing means will actuate therelay, thereby interrupting the circuit to the power outlet andcompleting a circuit through the alarm system, thus activating the saidalarm system.
 2. An alarm and safeguard system for a controlledenvironment box which includes, in combination: a. a main electricalpower source and a power outlet which connects into the said mainsource; b. a gas inlet line in communication with the environment boxand a source of inert gas; c. a gas outlet line in communication withthe environment box and a vacuum pump, the pump being electricallyconnected to the power outlet; d. a first solenoid valve located in thegas inlet line and a second solenoid valve located in the gas outletline; e. a first pressure switch which communicates with the environmentbox and Is electrically connected to the first solenoid valve and thepower outlet, for controlling inert gas flow into the environment box;f. a second pressure switch which communicates with the environment boxand is electrically connected to the second solenoid valve and the poweroutlet, for controlling inert gas flow out of the environment box; g. aninterchange chamber in communication with the environment box; h. anelectrical control system connected to the interchange chamber and tothe power outlet, for controlling evacuation and purging of theinterchange chamber; i. a manometer in communication with theenvironment box and which is electrically connected to the main powersource; j. an electrical relay which is connected to the main powersource and the power outlet; k. a first electrical sensing means, whichis associated with the manometer and is connected to the relay, forindicating a pressure condition in the environment box which does notcorrespond to a pre-set pressure condition; l. a second electricalsensing means which is associated with the manometer and is connected tothe relay, for indicating a pressure condition in the environment boxwhich does not correspond to the said pre-set pressure condition; m. analarm system which includes an audible signal and a visible signal, thesaid audible and visible signals being connected to the relay and to themain power source; whereby, when the pressure in the environment boxassumes a level other than the said pre-set pressure condition, at leastone of the said sensing means will actuate the relay, therebyinterrupting the circuit to the power outlet and completing a circuitthrough the alarm system, thus activating the said audible and visiblesignals.
 3. The alarm system of claim 2 in which: a. the manometer is aU-shaped manometer having one closed leg and one leg open to the outsideatmosphere; b. each leg of the manometer is partially filled withmercury; c. a first sensing wire is encased in the closed leg of themanometer and positioned such that the mercury in said leg will contactthe sensing wire and thus actuate the relay if the pressure in theenvironment box falls below the pre-set level; d. a second sensing wireis encased in the open leg of the manometer and positioned such that themercury in said leg will contact the sensing wire and thus actuate therelay if the pressure in the environment box rises above the pre-setlevel.
 4. The alarm system of claim 2 in which the audible signal is anelectric buzzer.